System of delivering and storing proppant for use at a well site and container for such proppant

ABSTRACT

A method of delivering proppant to a well site has the steps of transporting a load of proppant in a vessel to a desired location, moving the load of proppant from the vessel into a container so as to create a proppant-loaded container, unloading the proppant-loaded container into a pneumatic bulk trailer, and transporting the unloaded proppant in the pneumatic bulk trailer to well site. The container is placed onto a bed of a truck and moved in proximity to the vessel. The proppant-loaded container is placed onto a tilting mechanism and then tilted so that the proppant is discharged through a flow gate of a container into a hopper. The proppant in the hopper can then be conveyed to the pneumatic bulk trailer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patent application Ser. No. 13/332,937, filed on Dec. 21, 2011, and entitled “PROPPANT STORAGE VESSEL AND ASSEMBLY THEREOF”, presently pending.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIALS SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to proppant storage containers. More particularly, the present invention relates to systems and methods for the delivery of proppant to a well site. More particularly, the present invention relates to containers as part of a system of storing proppant prior to delivery to a well site.

2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.

Hydraulic fracturing is the propagation of fractions in a rock layer caused by the presence of pressurized fluid. Hydraulic fractures may form naturally, in the case of veins or dikes, or may be man-made in order to release petroleum, natural gas, coal seam gas, or other substances for extraction. Fracturing is done from a wellbore drilled into reservoir rock formations. The energy from the injection of a highly-pressurized fracturing fluid creates new channels in the rock which can increase the extraction rates and ultimate recovery of fossil fuels. The fracture width is typically maintained after the injection by introducing a proppant into the injected fluid. Proppant is a material, such as grains of sand, ceramic, or other particulates, that prevent the fractures from closing when the injection is stopped.

With the rise of hydraulic fracturing over the past decade, there is a steep climb in proppant demand. Global supplies are currently tight. The number of proppant suppliers worldwide has increased since 2000 from a handful to well over fifty sand, ceramic proppant and resin-coat producers.

By the far the dominant proppant is silica sand, made up of ancient weathered quartz, the most common mineral in the Earth's continental crust. Unlike common sand, which often feels gritty when rubbed between the fingers, sand used as a proppant tends to roll to the touch as a result of its round, spherical shape and tightly-graded particle distribution. Sand quality is a function of both deposit and processing. Grain size is critical, as any given proppant must reliably fall within certain mesh ranges, subject to downhole conditions and completion design. Generally, coarser proppant allows the higher flow capacity due to the larger pore spaces between grains. However, it may break down or crush more readily under stress due to the relatively fewer grain-to-grain contact points to bear the stress often incurred in deep oil- and gas-bearing formations.

Typically, in any hydraulic fracturing operation, a large amount of such proppant is required. Typically, it has been difficult to effectively store the proppant at the fracturing sites. Additionally, it has been found to be rather difficult to effectively transport the proppant to the desired location. Often, proppant is hauled to the desired locations on the back of trucks and is dumped onsite. Under such circumstances, the proppant is often exposed to adverse weather conditions. This will effectively degrade the quality of the proppant during its storage. Additionally, the maintenance of proppant in containers at the hydraulic fracturing site requires a large capital investment in storage facilities. Typically, the unloading of such storage facilities is carried out on a facility-by-facility basis. As such, there is a need to be able to effectively transport the proppant to and store the proppant in a desired location adjacent to the hydraulic fracturing location.

Present methods of storing proppant for use at the well site has involved a significant investment in structural facilities. In particular, silos have been built in order to store proppant for use in the fracturing operation. Often, the silos can have a cost of several million dollars. Whenever such silos are used, there is a possibility of contamination of the proppant that is contained within the silo. Large storage facilities often mix various types and qualities of proppant. As such, lower quality proppant may be mixed with higher quality proppant so as to create an undesirable contaminated combination.

The availability of high quality proppant is always of a major concern during such fracturing operations. If the proppant is not available at the well site, then the fracturing operation can stall until such time that proppant is available. In other circumstances, the operators of the fracturing operation may be forced to use lower quality proppant in order to continue the operation. As such, there is a need to be able to have high quality proppant available at all times during the fracturing operation. It is also important to provide a system which avoids the mixture of different types of proppant and to avoid the contamination of the proppant supply.

Under certain circumstances, railcars are used to deliver proppant to the fracturing location. The proppant is unloaded from the railcars into pneumatic bulk trailers. The pneumatic bulk trailers can then deliver the proppant to the well site. Often, the bulk materials train will have to remain on-site during the time the proppant remains in the bulk material train. As such, the train is not able to be used for other purposes. This adds additional cost to the fracturing operation. Ultimately, after the train is completely unloaded, a new bulk material train must be transported to the desired location and then serve as a storage facility. As such, a need is developed so as to quickly remove all of the proppant from the bulk material train and to store such proppant until such time as the proppant is needed.

In the past, various patents have issued relating to storage and transport facilities. For example, U.S. Patent Publication No. 2008/0179054, published on Jul. 31, 2008 to McGough et al., shows a bulk material storage and transportation system. In particular, the storage system is mounted on the trailer of a truck. The storage system includes walls that define an interior volume suitable for receiving the aggregate material therein. There are hoppers provided at the bottom of the container. These hoppers have inclined walls. The hoppers can extend so as to allow the material from the inside of the container to be properly conveyed to a location exterior of the container. Actuators are used so as to expand and collapse the container.

U.S. Pat. No. 7,240,681, issued on Jul. 10, 2007 to L. Saik, describes a trailer-mounted mobile apparatus for dewatering and recovering formation sand. The trailer is mounted to a truck-towable trailer so as to receive sand therein. The container has a pair of sloping end walls. The back end of the container is suitably openable so as to allow the sand to be removed therefrom. A pneumatic or hydraulic ram is provided on the forward part of the container so as to allow the container to be lifted angularly upwardly so as to allow sand to be discharged through the gate at the rear of the container.

U.S. Pat. No. 4,247,228, issued on Jan. 27, 1981 to Gray et al., describes a dump truck or trailer with a pneumatic conveyor. The container is mounted to a frame on wheels. A hydraulic ram tilts the container for dumping through a rear outlet. A pneumatic conveyor is carried by the frame with an intake at the rear of the container. A gate allows the solids to be dumped conventionally by gravity or to be blown to a storage facility by the pneumatic container. The container has a top hatch formed therein so as to allow the solids to be introduced into the interior of the container.

U.S. Pat. No. 2,865,521, issued on Dec. 23, 1958 to Fisher et al., shows a bulk material truck that has an interior volume suitable for the receipt of bulk material therein. A pneumatic conveyer is utilized so as to allow the removal of such material from the bottom of the container. A pair of sloping walls are provided on opposite sides of the container so as to allow the bulk material within the container to be passed toward the bottom of the container. A top hatch is provided on the top of the conveyer. The pneumatic conveyer is connected to the bottom of the container.

U.S. Pat. No. 4,995,522, issued on Feb. 26, 1991, to F. M. Barr, describes a bottom dumping bulk container apparatus for a bulk granulated material. The shipping container has a lower wall with a discharge opening. Doors are provided for the opening and closing of the discharge opening. The doors are actuated by an actuating structure which is mounted for vertical movement relative to the container. The actuating structure has upper portions which serve as conventional lifting connectors or receptacles at corners of the container. These cooperate with conventional hooks so that raising the actuating structure opens the door and lowering the actuating structure closes the door. This permits granulated material within the container to be dumped into a lower container or conveyance without requiring specialized lifting or opening equipment.

U.S. Pat. No. 6,401,983, issued on Jun. 11, 2002 to McDonald et al., provides a bulk cargo container for storing and transporting solid and liquid bulk materials. The bulk cargo container includes a vessel suitable for containing the bulk material and a supporting frame assembly having a generally horizontally-disposed support member attachment. The container portion is formed into at least one hopper having a discharge opening therein suitable for discharging bulk material contained within the vessel.

U.S. Pat. No. 4,138,163, issued on Feb. 6, 1979 to Calvert et al., discloses a bulk material container for the handling of flowable particulate materials. This container has a closed, generally rectangular parallelpiped structure with side walls, end walls and a roof. Conduits permit the introduction and withdrawal of particulate material to and from the container body. The lower base portion supports a vertical flexure panel at each corner thereof. The vertical flexure panel supports opposed pairs of longitudinal and transverse flexure panels between the tops thereof.

U.S. Pat. No. 4,909,556, issued on Mar. 20, 1990 to T. Koskinen, provides a transport container for the transport of bulk material. This transport container has a filling-hole in the upper part and an emptying device in the rear. For the loading and unloading, a side section is provided that can be opened. An emptying device, in the nature of a pneumatic pressure discharger, allows the material to freely flow from the containers through a check valve.

U.S. Pat. No. 7,967,161, issued on Jun. 28, 2011 to A. M. Townsend, provides a shipping container liner system for the shipping of bulk flowable materials. The system has a specially-adapted shipping container liner that is self-supporting without the need for rear-mounted rigid supportive bars to retain the liner within the shipping container during filling and discharge. The system has an arrangement of interior support baffles operating in conjunction with a plurality of exterior anchor straps adapted to distribute the cargo load throughout the length of the container.

U.S. Pat. No. 5,690,466, issued on Nov. 25, 1997 to Gaddis et al., shows slope plate for a particulate material truck box. The slope plate assembly includes a plurality of slope plate sections pivotally connected to the opposite side walls of the truck box so as to be movable between a raised inoperative position and a lowered operative position. In the lowered position, particulate material flows by gravity along the slope plate sections for discharge into an auger assembly residing below the floor of the truck box. In the raised position, bulk material or other cargo can be loaded into the truck box.

It is the object of the present invention to provide a system for the storage and transport of proppant that is mobile, scalable and flexible.

Another object to the present invention to provide a system for the storage and transport of proppant that can be located in proximity to the rail spur.

Another object of the present invention to provide a system for the transport and storage of proppant that can be rapidly implemented.

Another object of the present invention to provide a system for the storage and transport of proppant that occupies a small footprint.

The further object of the present invention to provide a system for the storage and transport of proppant that assures a continuous inventory of proppant to the fracturing operation.

Still another object of the present invention is to provide a system for the storage and transport of proppant that is movable and rechargeable at the drill site.

The further object of the present invention is to provide a system for the storage and transport of proppant that enhances the productivity of the proppant supplier.

The further object of the present invention to provide a system for the storage and transport of proppant that reduces driver fatigue.

Another object of the present invention to provide a system for the storage and transport of proppant that reduces liabilities.

The further object of the present invention to provide a system for the storage and transport of proppant that improves safety.

Further object of the present invention to provide a system for the storage and transport of proppant that is compliant with Department of Transportation regulations.

Still another object of the present invention to provide a system for the storage and transport of proppant which improves the profits for the proppant supplier.

These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.

BRIEF SUMMARY OF THE INVENTION

The present invention is an apparatus for proppant storage. This apparatus comprises a container having a bottom wall, a top wall, a pair of side walls, and a pair of end walls. The pair of side walls extend between the pair of end walls and between the bottom wall and the top wall. The container has an interior volume. A hatch is positioned on the top wall. This hatch is openable so as to allow the proppant to be introduced into the interior volume of the container. A flow gate is positioned on one of the end walls. The flow gate is openable so as to allow the proppant to flow outwardly of the interior volume of the container.

In the apparatus of the present invention, at least one of the end walls is recessed inwardly of the end of the pair of side walls and inwardly at the bottom wall and inwardly at the top wall. This end wall has a generally convex shape. A proppant inlet is affixed to the end wall. The proppant inlet communicates with the interior volume of the container. The proppant inlet is suitable for allowing proppant to be introduced into the interior volume of the container. A vent also opens to the interior volume. This vent is formed at an upper portion of one of the pair of end walls.

A longitudinal member is positioned in the interior volume of the container. The longitudinal member has one end affixed to one of the pair of end walls and an opposite end affixed to the other of the pair of end walls. A first cross member is positioned in the interior volume of the container. The first cross member has one end affixed to one of the pair of side walls and an opposite end affixed to the other of the pair of side walls. A second cross member is positioned in the interior volume of the container and in spaced relationship to the first cross member. The second cross member has one end affixed to one of the pair of side walls and an opposite end affixed to the other of the pair of side walls. A flow gate is positioned on one of the end walls generally adjacent to the bottom wall. This flow gate is slidable between an open position and a closed position.

The present invention is also a method of delivering proppant that comprises the steps of: (1) transporting a load of proppant in a vessel to a desired location; (2) moving the load of proppant from the vessel into a container so as to create a proppant-loaded container; (3) unloading the proppant-loaded container into a pneumatic bulk trailer; and (4) transporting the unloaded proppant in the pneumatic bulk trailer to a well site.

The vessel is a hopper of a bulk material train. The step of transporting includes loading the hopper with proppant in a remote location and then transporting the loaded proppant in the hopper of the bulk material train to the desired location. The step of moving includes conveying the proppant from the hopper of the bulk material train into a hatch formed at the top of the container.

The container can be placed onto the bed of a truck. The truck is moved so that the container is adjacent to the vessel. As such, the empty container is available so that the proppant can be conveyed from the hopper of the bulk material train into the interior volume of the container.

The step of unloading includes placing the proppant-loaded container onto a tilting mechanism, tilting the placed proppant-loaded container to an angle such that an end wall of the container faced downwardly at an angle, and discharging the proppant from the tilted container to a flow gate of the container. The proppant flows through the container of the flow gate into a hopper. This flowed proppant is conveyed from the hopper into the pneumatic bulk trailer. Air is injected into the container as the proppant flows through the flow gate. A plurality of the proppant-loaded containers can be stacked at the desired location prior to the step of unloading.

The present invention is also a method of delivering and storing proppant for use at the well site. This method includes the steps of: (1) transporting the load of proppant in a vessel to a desired location; (2) moving the load of proppant from the vessel into a plurality of containers so as to create a plurality of proppant-loaded containers; (3) stacking the plurality of proppant-loaded containers at the desired location so as to form a stack of the proppant-loaded containers; (4) lifting an upper most proppant-loaded container from the stack; (5) moving the upper most proppant-loaded container to a tilting mechanism; and (6) tilting the proppant-loaded container by the tilting mechanism so as to discharge the proppant from the container.

The discharged container can be transported to another stack of empty containers or to a position adjacent to the proppant-containing vessel. The proppant is discharged to a flow gate of the tilted proppant-loaded container into a hopper. The proppant from the hopper can be conveyed into a pneumatic bulk loader. The transported conveyed proppant in the pneumatic bulk trailer can then be transported to the well site.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a prospective view of the container apparatus as used in the system of the present invention.

FIG. 2 is an end view of the container apparatus as used in the system of the present invention.

FIG. 3 is an illustration of the system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is shown the proppant storage apparatus 10 in accordance with the preferred embodiment of the present invention. The proppant storage apparatus 10 includes a container 12 having a bottom wall 14, a top wall 16, a pair of side walls 18 and 20 and a pair of end walls 22 and 24. The side wall 18 extends between the bottom wall 14 and the top wall 16. The side wall 20 also extends between the bottom wall 14 and the top wall 16 in generally spaced parallel relationship to the side wall 18. The end wall 22 extends between the bottom wall 14 and the top wall 16. Similarly, the end wall 24 extends between the bottom wall 14 and the top wall 16 and also between the side walls 18 and 20. The top wall 16 has a hatch 26 formed thereon. Hatch 26 is openable so as to allow proppant to be introduced into the interior volume of the container 12. A flow gate 28 is positioned on the end wall 22. The flow gate 28 is openable so as to allow the proppant to flow outwardly of the interior volume of the container 12.

It can be seen that the end wall 22 is recessed inwardly of an end of the pair of side walls 18 and 20 and inwardly of the bottom wall 14 and the top wall 16. As such, the outermost end 30 of the container 12 will provide a protective structure for the generally convex surface of the end wall 22. This convex shape of the end wall 22 facilitates the ability to funnel the proppant from within the interior volume of container 12 outwardly through the flow gate 28. The frame structure at the end 30 enhances the structural integrity of the container 12 at this end while protecting the mechanical structures associated with the flow gate 28. The flow gate 28 is slidable upwardly so as to open to the interior volume. An inlet 32 is generally positioned at the end wall 22 and opened through the end wall 22 to the interior volume of the container 12. This proppant inlet is suitable for allowing proppant and/or air to be introduced into the interior volume of the container. As such, when the container 12 is at a well site or other location, additional proppant can be introduced into the interior volume of the container 12 through the proppant inlet 32. Inlet 32 also allows air to be introduced into the interior volume of the container 12 so as facilitate the ability of the proppant within the container 12 to exit through the flow gate 28. The inlet 32 is in the nature of a tube that can be connected to a suitable hose. A vent 34 is also positioned at the end wall 22. Vent 34 opens to the interior volume of the container 12 so as to allow excess air pressure to exit outwardly of the container 18.

The container 10 is configured so as to contain 96,000 pounds of proppant therein. Since each railcar can transport 192,000 pounds of proppant, a pair of containers 12 can receive all of the proppant from the railcar. However, conventional shipping containers could lack the structural integrity to contain such a large weight. As such, the proppant storage apparatus 10 includes an interior structure which enhances the integrity of the container 12 for its intended purpose.

In particular, a longitudinal member 36 is positioned in the interior volume of the container 12. Longitudinal member 36 extends generally centrally of the interior volume of the container 12. The longitudinal member 36 has one end rigidly affixed to the end wall 22 and an opposite end rigidly affixed to the end wall 24. This connection will maintain the integrity of the end walls 22 and 24 in spite of the large weight of proppant urging thereagainst. A first cross member 38 is positioned within the interior volume of the container 12. The first cross member 38 has one end affixed to the side wall 18 and an opposite end affixed to the side wall 20. A second cross member 40 is also positioned in the interior volume of the container and is in generally spaced parallel relationship to the first cross member 38. Each of the cross members 38 and 40 is positioned generally centrally with respect to the height of the container 12. The second cross member has one end affixed to the side wall 18 and an opposite end affixed to the side wall 22. The cross member 38 and 40 are configured so as to maintain the integrity of the side walls 18 and 20 against the large weight of proppant contained within the interior volume of the container 12.

FIG. 2 is an end view showing the proppant storage apparatus 10 of the present invention. In particular, the end wall 22 of the container 12 is illustrated as having a hatch 28 slidably received within guides 42 thereon. Suitable hydraulic or pneumatic mechanisms can be associated with the flow gate 28 so as to raise or lower the flow gate 28. In the lowered position, the flow gate 28 locks the flow of proppant from the interior volume of the container 12. In the raised position, the flow gate 28 will open to the interior volume of the container 12 so as to allow proppant to be discharged therefrom. The proppant inlet 32 and the vent 34 are illustrated as positioned on the end wall 22.

Within the concept of the present invention, it is important to be able to stack several containers on top of one another. As such, the end surface 30 has structural uprights 44 and 46 thereon. Similarly, horizontal structural members 48 and 50 will extend between the structural uprights 44 and 46 at the top and bottom of the container 12. The structural members enhance the integrity of the container so that a large amount of weight can be stacked upon the container 12. Again, the structural members 44, 46, 48 and 50 enhance the integrity of the container 12 to the heavy weight supported therein.

FIG. 3 shows a system 60 of the present invention. The system 60 initially involves the transport of a load of proppant to a desired location in a vessel 62. The vessel 62 is in the nature of hoppers associated with a bulk material train 64. The bulk material train 64 is driven by an engine 66 located on a rail spur 68. As such, in the present invention, the bulk material is delivered by the bulk material train 64 to the desired location. The vessel 62 of the bulk material train 64 can be immediately unloaded at this desired location so that the engine 66 can return the bulk material train 64 for other railroad usages.

The rail spur 68 is illustrated as being located in an elevated location. As such, containers 70, 72, 74 and 76 can be located in proximity to the vessel 62 and adjacent to the bulk material train 64. Each of the containers 70, 72, 74 and 76 has a configuration similar to that shown herein in association with FIGS. 1 and 2.

The hatch on the top wall 78 of the container 70 is illustrated as being adjacent to a conveyer 80 associated with the vessel 62. In other words, the hopper of the bulk material train 64 is opened adjacent to the conveyer 80. The conveyer 80 extends between the gate of the vessel 62 and the hatch at the top wall 78 of the container 70. Once this hopper of the bulk material train 64 is unloaded into the vessel 70, the conveyer 80 can be moved forwardly along the bulk material train 64 so that another hopper can discharge its proppant content into the container 72 of truck 82. The containers 70 and 72 are supported on the bed of the truck 82. Similarly, a conveyer 84 allows the unloading of another hopper of the bulk material train 64 into the container 74. The container 76 can be maintained in proximity to another hopper of the bulk material train 64 so that further unloading can occur.

A container loader/unloader 86 is positioned so as to allow for the lifting and transport of the containers 70, 72, 74 and 76. In particular, in FIG. 3, in can be seen that the container loader/unloader 86 has removed the containers from the truck 88 and has placed containers 92 and 92 upon tilting mechanisms 94 and 96, respectively. The tilting mechanisms 94 and 96 include a support panel that is pivotally connected to a frame. A hydraulic mechanism can then pivot the plate upwardly so that the container 90 is tilted so that the end wall faces at an angle downwardly toward a hopper 98. The tilting mechanism 96 also includes a similar structure such that the end wall of the container 92 is directed downwardly toward the hopper 100. The tilting mechanisms 94 and 96 allow proppant to be discharged in a very fast, convenient and safe manner into the respective hoppers 98 and 100.

A conveyer 102 extends to the bottom of the hopper 78 and to the top of a pneumatic bulk trailer 104. As a result, the proppant that is discharged through the flow gate at the end wall of the container 92 into the hopper 98 is transported by the conveyer 102 into the pneumatic bulk trailer 104. Similarly, another conveyer 106 extends from the hopper 100 to another pneumatic bulk trailer 108 so as to discharge proppant into the pneumatic bulk trailer. When each of the pneumatic bulk trailers 108 has been filled with proppant, these pneumatic bulk trailers 104 and 108 can then transport the proppant to the well site.

Flatbed trucks 110 and 112 are in line for receiving additional containers 114. Truck 112 is positioned adjacent to the container 114 so that the container loader/unloader 116 can place the containers onto the flatbed of the truck 112. Truck 112 can then move to another position adjacent to the bulk material train 64 for the further unloading of the hoppers associated therewith. As such, it can be seen that the staging of the various flatbed trucks allows for the efficient and effective removal of the proppant from the hoppers of the bulk material train 64.

Importantly, in FIG. 3, the containers 114 are arranged in a stacked configuration. The containers 114, as illustrated in FIG. 3, are stacked in a five-high stack since the containers are empty. However, within the concept of the present invention, if it is possible to unload the bulk material train 64 faster than the bulk material trailers 104 and 108 are available, then the filled containers can also be arranged in a stack. Typically, the containers can only be stacked four-high in view of large weight supported therein. These containers can be stacked until such time as proppant is required or until such time as equipment is available for the unloading of such containers.

Each of containers as utilized in the system of the present invention is a specially designed 8 foot by 20 foot container that is capable of containing 96,000 pounds of proppant. The containers can be moved by flatbed, low bed and container chassis that are accessible and economical. The facilities, such as illustrated in FIG. 3, requires only 1.5 acres to manage 45 million pounds of proppant. Empty containers can be stacked five-high and full containers can be stacked three or four high. Lashing can be used to ensure safety. The containers associated with the present invention allow proppant to be removed in an efficient and effective manner. Air can be injected through the inlet so as to facilitate the flow of proppant outwardly at the flow gate. In this arrangement, it has been found that 90,000 pounds of proppant can be unloaded in fifteen minutes.

Each of the containers can be arranged as to store 360,000 pounds of proppant per 160 square feet of footprint. The unloading equipment can unload one railcar in less then twenty minutes or unload a 120 car unit train in less then 48 hours. Multiple railcars can be unloaded at the same time.

The arrangement of containers is scalable for as much or as little proppant as required. A WMS inventory control system can be utilized. In such a system, each container can be bar-coded and logged-in to track the amount of proppant on hand by the mesh size of the proppant. Once the containers are loaded, they can be easily and safely stacked up in yards. As such, air space is utilized as opposed to yard space. All that is required is a solid foundation and proper container handling equipment.

The proppant is unloaded from containers to pneumatic bulk trailers. As such, the proppant will stay dry and would be manipulated less then flat-stored proppant. When the proppant is ordered, the container-moving machines move the container to hydraulic chassis. Proppant is then dumped into the hoppers. An airbox is utilized so as to blow the proppant out of the container.

The process of the present invention ensures close proximity of the site to the rail spur. The process of the present invention can be rapidly implemented when compared to silo facilities. Typically, such silo facilities can take up to two years to build. The number of containers is scalable for inventory requirements. A mini-stack of containers can be moved and recharged at the drill site so as to ensure continuous inventory for the fracturing operation. The system of the present invention can move the inventory closer to the production field then the prior art.

The present invention provides a lower overall cost per ton of proppant. In particular, the empty containers can be staged on-site at the mine. This serves to smooth out productivity for the proppant supplier. It also serves to improve throughput/profits for the proppant supplier. Any over supplies or leftover production can be stored on-site. This allows the company to negotiate better rates in exchange for helping the proppant supplier with their supply chain problems.

In contrast to prior systems where the pneumatic bulk trailer continually moves back and forth from the bulk material train to the well site, the present invention allows for the storage of such proppant in a location adjacent to the rail line. As a result, the truck drivers can have reduced fatigue. A safer work environment is promoted by the system of the present invention. A higher quality driver pool is maintained. Additionally, this system complies with Department of Transportation regulations.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction can be made within the scope of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents. 

I claim:
 1. An apparatus for proppant storage, the apparatus comprising: a container having a bottom wall and a top wall and a pair of side walls and a pair of end walls, said pair of side walls extending between said pair of end walls and between said bottom wall and said top wall, said container having an interior volume; a hatch positioned on said top wall, said hatch being openable to so as to allow the proppant to be introduced into said interior volume of said container; and a flow gate positioned on one of said of pair of end walls, said flow gate being openable so as to allow the proppant to flow outwardly of said interior volume of said container, said one of said pair of end walls being inset inwardly of an end of said pair of side walls and inwardly of an end of said bottom wall and inwardly of an end of said top wall.
 2. The apparatus of claim 1, said one of said pair of end walls having a generally convex shape.
 3. The apparatus of claim 1, further comprising: an inlet affixed to at least one of said pair of end walls, said inlet communicating with said interior volume of said container, said inlet suitable for allowing proppant or air to be introduced into said interior volume of said container.
 4. The apparatus of claim 3, further comprising: a vent opening to said interior volume, said vent formed at an upper portion of said one of said pair of end walls.
 5. The apparatus of claim 1, further comprising: a longitudinal member positioned in said interior volume of said container, said longitudinal member having one end affixed to one of said pair of end walls and an opposite end affixed to another of said pair of end walls.
 6. The apparatus of claim 1, further comprising: a first cross member positioned in said interior volume of said container, said first cross member having one end affixed to one of said pair of side walls and an opposite end affixed to the other of said pair of side walls.
 7. The apparatus of claim 6, further comprising: a second cross member positioned in said interior volume of said container and in spaced parallel relationship to said first cross member, said second cross member having one end affixed to the one of said pair of side walls and an opposite end affixed to the other of said pair of side walls.
 8. The apparatus of claim 1, said flow gate positioned on said one of said end walls generally adjacent said bottom wall, said flow gate being slidable between a closed position and an opened position. 